Pre-paid calling cards can be a convenient way to stay in touch. But the Federal Trade Commission, the nation’s consumer protection agency, and the Federal Communications Commission, the nation’s telecommunications agency, caution that hidden costs and other problems can leave consumers with less call time than they were promised.

The FTC offered this advice:

Look for added fees that may diminish the value of the card, like disconnect fees, maintenance fees, or pay phone surcharges.

Check whether the advertised minutes only apply if you make one call and not more.

Find out whether the advertised minutes still apply if you use the “toll-free access” number rather than the “local access” number, and whether the advertised minutes can be used to call cell phones.

Ask whether there is an expiration date for minutes.

Make sure that the explanation of fees makes sense to you.

If possible, select a card that comes with a toll-free customer service number.

Consider buying a card of a small denomination first, because if something goes wrong, your loss is limited.

The FTC works to prevent fraudulent, deceptive and unfair business practices in the marketplace and to provide information to help consumers spot, stop and avoid them. To file a complaint or get free information on consumer issues, visit ftc.gov or call toll-free, 1-877-FTC-HELP (1-877-382-4357); TTY: 1-866-653-4261. Watch a new video, How to File a Complaint, at ftc.gov/video to learn more. The FTC enters consumer complaints into the Consumer Sentinel Network, a secure online database and investigative tool used by more than 1,800 civil and criminal law enforcement agencies in the U.S. and abroad.